Field of the Invention
The invention relates to a process for the production of a multilayer coextrudate with a plastic layer that has release properties with respect to adhesives, where the materials producing the release properties are located within the plastic layer.
The purpose of the invention is to indicate a process of the kind outlined above with which a composite material consisting of a web, an adhesive, a release layer and a further web for the release layer can be produced in an efficient way.
In the solution to this problem proposed by the invention, a first web is provided in production of the coextrudate on one side of which a layer of adhesive is located, after which the plastic layer with the release properties follows, which is in turn bonded to a second web.
At least the basic structure of the composite material is produced in a single operation by this coextrusion process.
It has proved to be particularly favourable in this context if in accordance with a further development of the invention the layers of the coextrudate are coextruded simultaneously.
Particularly efficient production of the entire layer structure is achieved as a result.
In a particularly advantageous development of the invention, the layers are extruded simultaneously by the blown film process.
It is, however, also possible in accordance with a further development of the invention that the layers are produced by the cast film process.
In accordance with a further advantageous development of the invention, it is possible that a substrate web, to which the other layers are extruded in a single process operation, is provided as the first or second web.
This process is particularly favourable especially when a web is being used that is difficult or impossible to extrude at the same time, as all the other layers can be applied to the web that is acting as the substrate web in a single operation.
It is also very advantageous if in accordance with a further development of the invention a plastic film, to which the other layers are extruded in a single process operation, is provided as the substrate web.
A further advantageous development of the invention is characterised by the fact that at least the substrate web is oriented.
The coextrudate receives favourable strength properties as a result.
It is also possible in accordance with an advantageous development of the invention that the entire coextrudate is oriented.
All the layers that can be oriented can help to increase the strength properties in this case.
In accordance with an advantageous development of the invention, a multilayer coextrudate has at least two plastic films, between which a layer of adhesive and a further layer that has release properties with respect to the adhesive are located.
In a further advantageous development of the invention, further layers are provided that are located on either or both sides of the plastic films. Thus both elastic films are each provided with a further layer bonded to the plastic films.
It has proved to be very advantageous if in accordance with a further development of the invention at least part of the coextrudate structure is oriented.
Considerable increases in strength are achieved by orienting the substrate web or the finished coextrudate.